The present invention relates, in general, to fluid applicators and, in particular, fluid applicators of the type usable for intermittently dispensing a controlled amount of processing fluid across a photographic sheet material.
A variety of photographic processes of the self-developing type broadly involve the application of a viscous liquid reagent across exposed photographic sheet material in a predetermined thickness. One known self-developing type process includes exposing a photosensitive film sheet and then superimposing it with a second sheet. Prior to superimposing the two sheets a layer of processing fluid is deposited between the sheets in a thin layer. Superpositioning of the sheets and spreading of the fluid is accomplished by passing sheets between a pair of pressure-applying rollers which guide the sheets along convergent paths into superposition with one another. The spread fluid can initiate formation of visible images within either sheet.
Significant problems arise in connection with the metered application of such processing fluids. One problem is attributable to the fact that such fluids are readily oxidizable. Once oxidized the fluids can harden and, therefore, impede accurate dispensing. Also, such hardening could hamper significantly any desired sliding movement of parts which come into contact with the fluid. This problem is increased somewhat when it is intended to intermittently dispense measured amounts of the fluid over varying periods of time. Accordingly, it is crucial to protect the reagent against contact with the atmosphere when preserving the latter and insuring that build-up of hardened reagent is minimized or eliminated entirely. Moreover, it is significant that the reagent remain free from other contamination and that any hardened reagent not be dispensed onto the sheet.
Furthermore, it is, of course, desirable to achieve the foregoing with an applicator which is simple in construction, reliable in operation and serviced conveniently and quickly.
There have been several known approaches to overcoming the shortcomings inherent in dispensing such fluids. Representative examples of such approaches are disclosed in the following commonly-assigned U.S. Pat. Nos.: 2,435,719; 2,558,858; 2,563,343; 2,719,789; 3,120,792; 3,453,138; 3,142,242; 3,759,609; and 3,648,584.